Deadly Jellyfish Blooms Predictable, New Study Finds

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The key to predicting the presence of tiny, venomous and nearly
invisible jellyfish may be blowing in the wind, new research
finds.

The discovery, linking the appearance of teeny-tiny
jellies off the coast of Australia with wind patterns, could
lead to a way to prevent stings, researchers report today (May
13) in the Journal of the Royal Society Interface. Closing
beaches 31 percent of the time, when winds are inauspicious,
could reduce the number of stings by more than 61 percent, they
wrote.

The tiny jellies, called Irukandji jellyfish, are
transparent, and their bodies are so miniscule that they're
practically undetectable in the ocean. The largest species have
bodies only about an inch (2.5 centimeters) wide, while the
smallest are just a quarter of that size. [ See
Gorgeous Photos of Jellyfish Blooms ]

An initial Irukandji sting may be nearly imperceptible, but the
toxin can induce an illness called Irukandji syndrome, which
includes muscle aches, abdominal pain, nausea, vomiting, a racing
heart, high blood pressure and fluid buildup in the lungs. The
syndrome is often accompanied by an acute sense of anxiety, and
patients may feel they are doomed. In rare cases, the syndrome is
fatal.

Predicting jellies

In Australia, about 50 to 100 people are hospitalized each year
for Irukandji syndrome, and two people died from stings in the
Great
Barrier Reef in 2002. This danger has a ripple effect on
tourism and local economies, Lisa-ann Gershwin, a scientist at
the Commonwealth Scientific and Industrial Research Organization
in Australia, and her colleagues wrote in the new study.

Local lore has long held that stings are most common when
northeasterly winds are low. Gershwin and her colleagues decided
to test that notion, comparing records of sting times and
locations with wind estimates between January 1985 and August
2012.

Their results revealed that the locals are partly right. Winds do
affect the risk of Irukandji stings. In fact, the highest risk
comes not when northeasterly winds are low, but when the
southeasterly trade winds drop off temporarily (a related
phenomenon).

Sting prevention

Next, the researchers plotted out the results of using the winds
as a way to inform beach closures. They found that closing
beaches in response to a decline in southeasterly wind speeds
would have prevented some stings.

The strength of the effect, of course, depends on how
conservative officials are about closing beaches. For example,
closing the beach for a single day when the winds revert from
southeasterly to northeasterly would require shutting down
beaches 31 percent of the time and would reduce the number of
days with stings by 61 percent. (Jellies sting more than one
swimmer about a third of the days when someone is stung, so the
total number of injuries prevented would be higher.) Closing the
beaches 64 percent of the days would cut down the number of days
with stings to 90 percent.

Southeasterly winds produce lots of turbulence near the shore and
also
cause downwelling, pushing water offshore. Jellies are
drifters, so they're unlikely to fight the current, the
researchers wrote; thus, when the southeasterly trade winds are
strong, Irukandji jellyfish likely go with the flow, away from
beachgoers. When the winds are low, turbulence and downwelling
decrease, allowing more jellies to drift toward shore. Sea
breezes, which blow from the ocean inland, likely enhance this
landward movement.